This section is intended to introduce the reader to various aspects of art, which may be related to various aspects of the present invention that are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Communication systems are generally subject to transmission errors. In broadcast systems, error correction is used to improve transmission robustness. Forward Error Correction (FEC), based on the addition of redundant information, performs error correction without the need of repeating information and without using a return channel. FEC is commonly used on communication networks, such as terrestrial, mobile or satellite networks. Another correction mode uses repetition, where data is sent several times to the receivers. Repetition may be performed on demand from a receiver, where the receiver detects an error and requests repetition to the transmitter. This is possible when a return channel is available. The return channel is used by a receiver to send a request to the transmitter for repeating lost or corrupted information.
In the digital television domain, television decoders, also called set-top boxes, are used to access a set of television channels that are transmitted with encryption and that are decrypted within the decoder. Television decoders are the interface units between the television signal transmission systems, notably digital television signals in MPEG and DVB format, and the display monitors. The transmission means that broadcast the television transmissions to these decoders can be standard aerial transmission means, coaxial cables, optical cables, re-transmission satellites serving a region, or the Internet network. The decoder comprises the reception means to receive the transmitted signals and the formatting means to transform the received signals into signals that can be directly applied to the display device command units. The decoder also usually comprises error detection and error correction means. They are bound to the broadcast transmission means. In particular, in a satellite transmission system, the forward error correction may be used. In a transmission over the Internet Protocol, retransmission may be used.
Set-top boxes are today adapted to receive content from at least two networks, such as the Internet and the terrestrial transmission system. Broadcast video is usually transmitted in the broadcast network, the Internet network being used for interactive services. When receiving video content from the unidirectional terrestrial distribution network, the forward error correction mechanism available on that distribution network is used. However transporting FEC packets may be burdensome and costly for the distribution network. It would be valuable to minimize the impact of the error control over the broadcast network.